Foundation: fixture specification and validator #65

Goal

One fixture format across sixty recipes, checked by a tool, so fixtures stay readable and honest.

Scope

• A written specification for fixtures/: inputs, gold labels, and model responses, in JSON or JSON Lines, with stable identifiers linking the three.
• Split support (validation, test, and others as needed) recorded per example.
• Required provenance on every response: synthetic or recorded, plus model string and date when recorded.
• A JSON Schema and a validator: python -m jev_cookbook.fixtures validate recipes/NN-slug.
• Checks beyond schema: every evaluated input has a label, identifiers are unique, no response without a matching input, and a scan for strings that look like keys or tokens.

Acceptance criteria

• Validator passes on a good example and fails with a specific message on each kind of bad one, with tests for both
• The specification is one page in docs/ and is linked from CONTRIBUTING.md
• The validator exits non-zero on failure so CI can use it
• Lint and tests pass in CI, or locally with the output pasted in the pull request if CI does not exist yet

Dependencies

• Blocked by Foundation: decision backends with typed answers, replay, and scripted modes #63 (decision backends with typed answers, replay, and scripted modes)
• Unblocks Foundation: recipe template and scaffolder #68
• Tracked in Epic: Foundation #74

References

• Recipe contract
• Catalog
• TypeSafe documentation index for tools: https://docs.typesafe.ai/llms.txt
• Python SDK: https://docs.typesafe.ai/sdk/python